Movement of Traction Drive Motor for EV/HEV: High Performance Design-concept and Issues of Permanent Magnet Motor for Toyota Prius

摘要

Permanent magnet motors were improved remarkably, after Nd-Fe-B magnets were invented in the first half of the 1980's, and high power semi-conductor has made progress. Since then permanent magnet motors for EV/HEV traction drive have been developed rapidly with high performance of output. The reason is because it is attempting the optimization of the system-wide driving force which included the final gear ratio of running drive of cars such as engine and reduction gear in addition to motor design technique as electrical appliance. Figure 1 shows the cut model photograph of the trans-axle which introduced into Toyota Prius from the 1st generation to the 3rd generation, and the concept of the motor downsizing. The motor size is 38 % smaller in the 2nd generation and moreover 74 % smaller in the 3rd generation than that in the 1st generation. We have make progress in downsizing with the three concepts as follows. The first is Nd-Fe-B magnets with high performance, the second is higher system voltage, the third is higher rotation speed. In the motor specification of the 3rd generation Prius, the system voltage is 650V and the maximum rotation speed is 13500rpm.